The invention is directed generally to novel polyolefin compositions having enhanced resistance to ultraviolet (UV) exposure and oxidative conditions and to methods for producing and using the same. More specifically, the invention relates to catalyst dispersing carriers and to dicyclopentadiene polymers (poly-DCPD) produced using metathesis catalysts that have been dispersed in a dispersing carrier.
It is known to use certain ruthenium and osmium carbene compounds to catalyze olefin metathesis reactions such as, for example, ring opening metathesis polymerization (ROMP), to produce polyolefin compositions. Such olefin metathesis reactions and suitable metathesis catalysts (e.g., ruthenium- or osmium-based catalysts) have been previously described in, for example, U.S. Pat. Nos. 5,312,940, 5,342,909, 5,728,917, 5,710i298, 5,831,108, and 6,001,909; PCT Publications WO 97/20865, WO 97/29135 and WO 99/51344; in United States Provisional Patent Application No. 60/142,713 filed Jul. 7, 1999 entitled xe2x80x9cROMP Reactions Using Imidazolidine-Based Metal Carbene Metathesis Catalysts;xe2x80x9d and by Fxc3xcrstner, Picquet, Bruneau, and Dixneuf in Chemical Communications, 1998, pages 1315-1316, the disclosures of each of which are incorporated herein by reference.
One example of a polyolefin compound that may be produced using the aforementioned metathesis catalysts is poly-DCPD. A problem associated with the polymerization of DCPD is obtaining a homogeneous mixture of metathesis catalyst with DCPD monomer. It has been found that, in order to obtain the desired catalyst:DCPD monomer ratio, it is preferable to pre-mix the catalyst in a small amount of DCPD monomer prior to introduction to and mixing with the remaining amount of DCPD monomer. Such pre-mixing leads to a more homogeneous dispersion of the catalyst in the DCPD monomer and ensures that the catalyst and the monomer are combined in their proper proportions in order to optimize the polymerization reaction. However, it has been determined that poly-DCPD compositions prepared using these catalyst-DCPD mixtures suffer a rapid loss of physical properties, particularly impact properties, with aging. This deterioration is even more pronounced in the presence of ultraviolet (UV) exposure or under oxidative conditions, and is particularly severe in the case of UV weathering with condensation. The deterioration rate can be reduced by the addition of certain traditional antioxidant materials such as, for example, 4,4xe2x80x2-methylenebis(2,6-di-tertiary-butylphenol) (Ethanox 702(trademark); Albemarle Corporation), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene (Ethanox 330(trademark); Albemarle Corporation), and octadecyl-3-(3xe2x80x2, 5xe2x80x2-di-tert-butyl-4xe2x80x2-hydroxyphenyl)propionate (Irganox 1076(trademark); Ciba-Geigy). However, these traditional antioxidant materials are typically very expensive.
In light of the foregoing, there exists a need for a means to homogeneously disperse a metathesis catalyst in an olefin (e.g., DCPD) monomer prior to polymerization and for an effective and inexpensive way to enhance the UV and oxidative resistance of the resulting polyolefin (e.g., poly-DCPD) composition.
The invention relates to novel polyolefin compositions having enhanced UV and oxidative resistance and methods for their production and use. In particular, the invention provides for a dispersing carrier in which a metathesis catalyst may be dispersed prior to mixing with an olefin monomer, in order to optimize the catalyst:olefin monomer ratio as well as to obtain a sufficiently homogeneous catalyst-monomer mixture prior to polymerization.
The dispersing carrier may be any solvent which has a sufficiently high viscosity so as to permit effective dispersion of the catalyst, and which is sufficiently inert and which has a sufficiently high boiling point so that it does not act as a low-boiling impurity in the olefin metathesis reaction. Particularly preferred catalyst dispersing carriers include xe2x80x9coilyxe2x80x9d or hydrophobic solvents such as, for example, soybean oil or mineral oil. Other preferred catalyst dispersing carriers include high-viscosity hydrophobic hydrocarbons such as, for example, tri-isopropylbenzene (SureSol 450(trademark)).
The dispersion of the metathesis catalyst in a catalyst dispersing carrier prior to polymerization permits a sufficiently homogeneous catalyst-monomer mixture. In addition, the catalyst dispersing carrier unexpectedly produces a polyolefin composition having enhanced resistance to UV exposure and oxidative conditions. Specifically, the catalyst dispersing carrier reduces the rate of deterioration of physical properties with aging. The increase in UV and oxidative resistance provided by the dispersing carrier obviates the need for the addition of traditional, expensive antioxidant materials.
One aspect of the invention is a novel polyolefin composition having enhanced UV and oxidative resistance without the need for typical antioxidants. Another aspect is a process for preparing such UV-resistant polyolefin compositions, wherein the process includes the step of dispersing a metathesis catalyst in a catalyst dispersing carrier prior to mixing with the olefin monomer. Yet another aspect is a polyolefin composition prepared using the aforementioned process. A further aspect is an article of manufacture comprising the aforementioned polyolefin composition, such article having enhanced UV and oxidative resistance. These and other aspects of the invention will be apparent to one skilled in the art in light of the figures and the following detailed description of the preferred embodiments.